Personal finance guides in plain words
One concept per guide, answered in the first paragraph, with a working calculator on the same screen. No account needed for any of it.
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Class and household
How budgeting works: plan, split, saving rate
What a budget is for, fixed against variable costs, where the 50/30/20 rule breaks down, zero-based budgeting, and what a saving rate does and does not predict.
Emergency funds: how to size and build one
What an emergency fund covers, how to size it from your own essential monthly costs rather than a generic month count, and why it stays liquid even at a lower rate.
How credit scores work and what moves them
What a credit score measures, which factors carry the most weight, why utilisation is the fastest lever a borrower has, and how a score differs from debt-to-income.
How credit cards charge interest
How a card turns an APR into a daily rate, why paying the statement balance in full usually costs nothing, what a partial payment does, and why cash advances start charging at once.
How student loans work in the United States
How interest accrues before repayment starts, what capitalisation adds to the balance, why a standard and an income-driven plan produce different totals, and what refinancing gives up.
What net worth means and how to track it
Net worth is what you own minus what you owe. Which assets to count and at what value, whether a home and a car belong on the list, and why the trend beats one reading.
How FICA and take-home pay work
FICA is 6.2 percent Social Security plus 1.45 percent Medicare. On a \$2,000 weekly check with 12 percent federal withholding, take-home is \$1,607.
How credit utilization works
Credit utilization is the reported revolving balance divided by the revolving limit. \$2,400 on an \$8,000 limit is 30 percent, and paying in full may still show a balance.
How compound interest works
Interest that earns interest, explained with worked numbers: the formula, what an early start is really worth, the rule of 72, and what compounding frequency changes.
Borrowing and credit
How a mortgage works, from lien to payment
What the lender's lien actually secures, how loan to value and escrow work, what discount points buy, and why the first years of a mortgage are almost all interest.
How amortisation works, payment by payment
Why a level loan payment is nearly all interest at the start, how the split shifts every month, what an extra payment removes, and what a shorter term does.
How extra mortgage payments work
What an extra amount paid against principal does to a mortgage: months taken off the term, interest not paid, and why the first extra dollars buy more time than the later ones.
How private mortgage insurance works
PMI is a lender-required premium when the down payment is under 20 percent. What it is charged on, when it cancels at 80 percent of original price, and why it is not a higher mortgage rate.
How mortgage points work
Discount points are prepaid interest paid at closing to cut the contract rate. How the cash-flow break-even is counted in months, and why refinancing resets that clock.
Payday loans and high cost credit
Why a fee that looks small over two weeks annualises into a triple digit APR, how the rollover cycle repeats it, and what the alternatives actually cost.
Saving and planning
How present value works
Present value is what a future cash flow is worth today at a stated rate. How discounting undoes growth, how a payment stream is a stack of lumps, and why the rate and the period have to match.
How FIRE numbers work
A FIRE number is annual spending divided by a withdrawal rate. Why 4 percent is 25 times spending, how years to the pile are counted at one constant return, and what the identity is silent on.
Investing
Risk and return: the trade-off explained
Why higher expected return demands more risk, what risk means as a spread of outcomes, how the risk premium sits above the risk-free rate, and what volatility costs.
How diversification lowers risk
Why holding assets that do not move together lowers risk without lowering expected return, what correlation means in plain words, and what diversification cannot protect you from.
Index funds vs active management
Why the average actively managed dollar trails the market by its costs, what an index fund actually holds, and what one point of yearly fee does over 30 years.
How stocks work: shares, profit and price
What a share of stock actually is: a claim on the profit left after everyone else is paid, why dividends and retained earnings are the same dollar, and what a price represents.
How bonds work: coupon, price and yield
What a bond is, how face value, coupon and maturity fit together, why prices fall when interest rates rise, what duration measures, and where bondholders rank if a borrower fails.
How two-stage DCF works
Two-stage DCF values a firm as an explicit free-cash-flow forecast plus a Gordon-growth terminal value. Why most enterprise value sits after the forecast, and why growth must stay below WACC.
How the price to earnings ratio works
P/E is share price divided by earnings per share. A \$50 share on \$2.50 of earnings is 20 times, and a lower P/E is not always a cheaper share.
How cap rates work
Cap rate is net operating income over price. The same income at a comparison cap is a value, which is how two properties are compared without mixing in a mortgage or a tax bracket.
Corporate finance
How WACC is calculated
The weighted average cost of capital blends equity and after-tax debt by market value. The WACC formula, the tax term on debt, and why cheaper debt does not stay cheaper as the mix shifts.
How NPV and IRR work
NPV and IRR are one equation asked two ways: a value at a rate you choose, or the rate that drives that value to zero. They agree on accept or reject. Ranking is a different question, and NPV decides.
How the leverage ratio works
The three leverage ratio formulas from one balance sheet: debt-to-equity, debt-to-assets and the equity multiplier, plus what a fall in asset values does to equity.
How return on equity (ROE) works
ROE is net income over book equity. On \$15,000,000 of profit and \$100,000,000 of equity it is 15 percent, and financial leverage sits inside that rate.
How the cash conversion cycle works
CCC is days sales plus days inventory, minus days payable. 45 plus 60 minus 30 is 75 days, and a negative cycle means suppliers are funding the firm.
How interest coverage works
Interest coverage is EBIT divided by interest expense. On \$80,000,000 of EBIT and \$10,000,000 of interest it is 8 times, and a zero interest line is not infinity.
Cost of capital: the rate a project clears
The cost of capital is the return an investment must beat, not a bill a company pays. Why equity costs more than debt, what the interest deduction is worth, and where one firm-wide rate misleads.
How to read financial statements
The three statements and what each answers: the balance sheet at one date, the income statement over a period, and the cash flow statement that shows why profit is not cash.
Taxes and retirement
Tax-advantaged accounts: how they work
How tax deferred and tax exempt accounts differ, why sheltering the growth does most of the work, and how to weigh paying tax now against paying it later.
How 401(k) matching works
A 401(k) match is a stated rate on a stated slice of pay. How the cap works, what is left unclaimed if you defer less, and what that leftover stream grows to if it is invested.
Safe withdrawal rates and what they assume
What a safe withdrawal rate is, the historical backtests it comes from, and the assumptions that move it: horizon, allocation, fees, taxes and whether spending flexes.
How sequence of returns risk works
The order returns arrive in changes nothing while a portfolio sits still, and a great deal once you withdraw from it. Worked numbers, and why the years around retirement matter most.
How investments are taxed
Income against capital gains, realised against unrealised, why a holding period can change the rate, why funds distribute gains you did not choose, and what a wrapper changes.
More explainers
How annuities work
An annuity swaps a sum of money for an income. How the pool pays, why a payout rate is not a return, and what fixed, variable and deferred contracts each change.
Asset allocation: how the mix drives risk
How a portfolio splits across stocks, bonds and cash, why the mix explains most of the variation in returns over time, and how horizon and risk capacity set it.
Behavioural biases in money decisions
Loss aversion, mental accounting, anchoring, recency, confirmation and sunk cost, each with a money example, and why rules set in advance beat willpower.
Car finance, depreciation, negative equity
Why a loan against a car that is losing value turns into negative equity, how depreciation front-loads, what a longer term really costs, and what the payment hides.
Credit reports and how to fix errors
What a United States credit report contains, who supplies the data, why errors are common, and how a dispute works with both the agency and the company that reported it.
Debt snowball vs avalanche: the numbers
The avalanche pays the highest rate first and the snowball the smallest balance first. Two cards, one budget, both orders run in full, and what sets the size of the gap.
Dollar cost averaging, explained
Buying a fixed amount on a schedule: why the cost per unit lands at or below the average price, why investing a lump sum at once usually finishes ahead, and what spreading buys.
Financial ratios, and what they miss
The four families of financial ratio, what each one answers, and why nearly every ratio needs a comparable before it means anything: the same company last year, or a rival.
Inflation and purchasing power explained
What inflation does to money over time, why a real return divides rather than subtracts, and how an account paying under inflation loses ground while the balance rises.
Insurance and risk pooling explained
How pooling independent risks makes an unpredictable loss predictable for the group, why cover can still be worth buying when it loses money on average, and what deductibles change.
What investment fees really cost
Percentage fees are charged on your balance, not your gain, so they are paid in losing years too. What expense ratios, platform fees, spreads and advice fees really cost over time.
Life and disability insurance explained
Who needs life cover and who does not, why level term is the usual starting point, why a long disability is the more likely claim, and how to reason about the amount.
Opportunity cost of money: what you give up
Every dollar has a next best use. How to price what a purchase, a cash pile or an unpaid debt gives up, how to pick the rate you compare against, and when to bother.
How portfolio rebalancing works
Rebalancing sells what has grown and buys what has not, to restore a target mix. Why drift raises risk silently, calendar against threshold rules, tax friction, and what it really pays.
Renting against buying a home
What each side costs and never returns, why the mortgage payment is the wrong number to compare, how the break-even horizon works, and what borrowing does to the risk.
Types of savings account, compared
Checking, savings, high-yield savings, money market accounts and certificates of deposit: what each one trades away for a higher rate, and why the yield beats the rate.
The yield curve: shape, slope and inversion
What the yield curve plots, why it normally slopes up, what an inverted curve says about future interest rates, and how much weight its recession record deserves.
Time value of money: present and future value
Why a dollar today is worth more than a dollar later, and by how much. Present value, future value, discount factors and how to pick the rate that prices the wait.
Volatility drag: why averages overstate growth
Why a run of returns that varied compounds to less than its arithmetic average, why the gap grows with the square of the spread, and why a fund tracking twice an index daily misses over a year.
What a stock index is, and how it is weighted
A stock index is a rule for choosing companies and weighting them. How market value, price and equal weighting differ, what reconstitution changes, and why an index is not the economy.
What liquidity means in finance
How fast an asset turns into cash without moving its price, why illiquid assets can pay more, and why running out of cash is not the same as running out of value.